Research progress of active compounds and pharmacological effects in Akebia trifoliata (Thunb) koidz stems

Germplasm resources and genetic improvement of Akebia: A new fruit crop in China

Akebia species, belonging to Lardizabalaceae, are widespread from subtropical to temperate environments of China, Japan, and Korea. All known Akebia species have medicinal and dietary value and have been widely cultivated as a new fruit crop in many areas of China. However, compared with other crop species, the breeding improvement and commercial cultivation of Akebia remain in their infancy. This review systematically introduces the present germplasm resources, geographical distribution, biological characteristics, interspecific and intraspecific cross compatibility, molecular biology, and breeding progress in Akebia species. Akebia plants are widely distributed in Shanxi, Henan, Sichuan, Chongqing, Hunan, Hubei, Jiangxi, Zhejiang, and Fujian provinces of China, and wild Akebia plants exhibit abundant phenotypic and genetic diversity due to their wide range of geographical distribution and high adaptability in different habitats. Interspecific artificial hybridization experiments have been conducted in our Akebia germplasm resources nursery. The results showed that there was no reproductive isolation between Akebia species, and fertile progeny could be produced. The synthesis of knowledge on these species provides insights for the rational development and utilization of these germplasm resources, and can facilitate the development of new breeding lines or varieties for commercial cultivation or production. Finally, perspectives on Akebia breeding research are discussed and conclusions are provided. This review provided breeders with new insights into Akebia domestication and breeding, and we also proposed five basic steps in the domestication of new fruit crops.

Genome-Wide Identification and Expression Analysis of WRKY Transcription Factors in Akebiatrifoliata: A Bioinformatics Study

WRKY transcription factors have been found in most plants and play an important role in regulating organ growth and disease response. Outlining the profile of WRKY genes is a very useful project for studying morphogenesis and resistance formation. In the present study, a total of 63 WRKY genes consisting of 13 class I, 41 class II, and 9 class III genes were identified from the newly published A. trifoliata genome, of which 62 were physically distributed on all 16 chromosomes. Structurally, two AkWRKY genes (AkWRKY6 and AkWRKY52) contained four domains, and AkWRKY17 lacked the typical heptapeptide structure. Evolutionarily, 42, 16, and 5 AkWRKY genes experienced whole genome duplication (WGD) or fragmentation, dispersed duplication, and tandem duplication, respectively; 28 Ka/Ks values of 30 pairs of homologous genes were far lower than 1, while those of orthologous gene pairs between AkWRKY41 and AkWRKY52 reached up to 2.07. Transcriptome analysis showed that many of the genes were generally expressed at a low level in 12 fruit samples consisting of three tissues, including rind, flesh, and seeds, at four developmental stages, and interaction analysis between AkWRKY and AkNBS genes containing W-boxes suggested that AkWRKY24 could play a role in plant disease resistance by positively regulating AkNBS18. In summary, the WRKY gene family of A. trifoliata was systemically characterized for the first time, and the data and information obtained regarding AkWRKY could be very useful in further theoretically elucidating the molecular mechanisms of plant development and response to pathogens and practically improving favorable traits such as disease resistance.

The Akebia Genus as a Novel Forest Crop: A Review of Its Genetic Resources, Nutritional Components, Biosynthesis, and Biological Studies

The genus Akebia belongs to the Lardizabalaceae family and comprises five species that are primarily distributed in East Asia. Plants of the Akebia genus comprise deciduous and semi-evergreen perennial twining vines that have been used in Chinese herbal medicine for at least 2000 years. The plants of this genus have the potential to form a novel forest crop with high nutritional and economic value because their fruit has a delicious sweet taste and rich nutrient components. In this study, we organized, analyzed, and evaluated the available published scientific literature on the botanical, ecological, and phytochemical characteristics of Akebia plants. Based on these studies, we briefly introduced botanical and ecological characteristics and focused on reviewing the development and utilization of wild genetic resources in the genus Akebia. We further explored the genus' rich nutritional components, such as triterpenes, flavonoids, polyphenols, polysaccharides, and fatty acids, and their potential use in food and health improvement applications. In addition, several papers describing advances in biotechnological research focusing on micropropagation, nutrient biosynthesis, and fruit ripeness were also included. This review provides comprehensive knowledge of the Akebia genus as a new forest crop for food and fruit utilization, and we also discuss future breeding and research prospects.

Akebia quinata and Akebia trifoliata - a review of phytochemical composition, ethnopharmacological approaches and biological studies

ETHNOPHARMACOLOGICAL RELEVANCE

'Akebia stem' (Akebiae caulis) is one of the newest raw materials officially introduced into therapeutic practice from traditional Chinese medicine. A monograph on this material appeared for the first time in 2018 in Supplement 9.6 to the 9th edition of the European Pharmacopoeia. In the latest 10th edition of the European Pharmacopoeia, the monograph remained unchanged. The 'Akebia stem' monograph allows the use, as a raw material, of Akebia quinata (Houtt.) Decne., A. trifoliata (Thunb.) Koidz, or a mixture of the two species.

AIM OF THE STUDY

The aim of this work is a detailed review of the scientific literature on the genus Akebia (family Lardizabalaceae), with particular emphasis on A. quinata and A. trifoliata, providing information on the botanical, ecological, and chemical characteristics of these species. Professional research on their biological activity has been reviewed. The attention is given to phytochemistry and cosmetology. The traditional use of Akebia species and their potential use in medicine and cosmetology are assessed. In addition, individual papers describing biotechnology research on in vitro cultures of the two Akebia species are presented.

MATERIALS AND METHODS

The presented botanical, ecological, phytochemical and biotechnological characterization is based on a thorough review of published scientific research. It is a compilation and evaluation of data on the chemical composition and biological activities of these Akebia species.

RESULTS

This critical review of phytochemical studies demonstrates that triterpenoid saponins are dominant secondary metabolites of these species. A comparative analysis of phytochemical studies on A. quinata and A. trifoliata stems, roots, fruits, and seeds showed differences in metabolites based on the plant parts and species. The triterpenoid saponins mutongsaponin C and saponin P_j1 have been found only in A. trifoliata, whereas the phenolic glycoside 2-(3,4-dihydroxyphenyl)-ethyl-O-β-D-glucopyranoside has been found only in A. quinata. Biological activity studies of A. quinata stem, leaf and/or fruit extracts have confirmed diuretic, hepatoregenerative, neuroprotective, analgesic, anti-inflammatory, and anti-obesity effects and an influence on ethanol metabolism. Different action profiles have been demonstrated for A. trifoliata stem, leaf and/or fruit extracts. Studies have proven the antibacterial and anticancer (liver and stomach) effects of these species. This review presents potential phytopharmacological applications of both species and detailed data on their broad applications in cosmetology. Attention is also drawn to information on the safety of using Akebia. Finally, an overview of biotechnology research on both species is presented.

CONCLUSIONS

This review provides comprehensive knowledge about the ethnopharmacological use of Akebia species. Moreover, new findings on the differences in the chemical composition and biological activity profiles are underlined.